加固改造中的结构承重体系转换

从加固改造工程的实践出发 ,探讨了混合结构向框架结构体系转换的方法和构造措施 ,为实际工程提供了新的技术思路     

Further evidence of responsibility of impurities in MgO for variability in its basicity and catalytic performance in oxidative coupling of methane

Further evidence was delivered that certain impurities, which could be contained in MgO samples, might be responsible for observed variability in MgO basicity and catalytic performance in oxidative coupling of methane. The surface basicity/base strength distribution of a series of MgO samples containing or not containing Ca and Na impurities was determined by a temperature-programmed desorption of CO₂. It was revealed that samples containing Ca and Na impurities have much more medium, strong and very strong basic sites. The surface basicity of MgO samples containing added alkali or alkaline earth compounds or water was characterized by a test reaction of transformation of 2-butanol. It was confirmed that the introduction of these compounds to a pure MgO enhanced both its basicity and activity in oxidative coupling of methane.     

激光冲击诱发相变的实验研究

本对激光冲击是否可以诱发相变进行了试验研究。用功率密度为１．０６×１０＾８Ｗ／ｃｍ＾２的激光器冲击Ｔ８钢表面。实验结果表明激光冲击处理使Ｔ８钢的表面显微硬度有所提高并可以发生马氏体相变。冲击处理后材料表面硬度提高了两倍，认为相变是Ｔ８钢表面硬度提高的原因之一。     

Finite elements in the analysis of pressure vessels and piping-a bibliography (1976–1996)

The paper gives a bibliographical review of the finite element methods (FEMs) applied for the analysis of pressure vessel structures/components and piping from the theoretical as well as practical points of view. The range of applications of FEMs in this area is wide and cannot be presented in a single paper; therefore the aim of this review is to give the reader an encyclopaedic view of the differnt possibilities that exist today for the finite element analysis in the fields of pressure vessels and piping. The bibliography at the end of the paper contains approximately 1900 references to papers, conference proceedings and theses/dissertations on the subject that were published in 1976–1996. These are classified in the following categories: linear and non-linear, static and dynamic, stress and deflection analysis; stability problems; thermal problems; fracture mechanics problems; contact problems; fluid-structure interaction problems; manufacturing of pipes and tubes; welded pipes and pressure vessel components; development of special finite elements for pressure vessels and pipes; finite element software; and other topics. Also finite element software, general purpose and special purpose codes, used for the analysis of pressure vessels and pipes are briefly discussed and presented.     

Observation of atomic steps on CaCO3 crystal surface

By using scanning polarization force microscopy,the deliquescence process and the atomic steps on the cleavage surface of CaCO3 in air were studied in situ.Under an exposure to medium umidity(-57%),the sloiw step movement has been observed.     

轴端沟槽底部激光强化工艺参数优化研究

分析了选用不同激光能量密度对HT300进行表面强化处理时，材料表面呈现的四种状况；未相变硬化、相变硬化、表面微熔与表面熔凝的金相组织。根据工艺要求，选取相变硬化方法对轴端沟槽底表面进行处理。分析了工件激光处理方法并通过试验研究，寻找轴端沟槽底部激光强化工艺参数；激光功率（P）、光斑直径（D）及扫描速度（V）的优化组合。硬度测试及耐磨性能试验表明：激光相变处理和激光熔凝处理后轴端沟槽底部表面较表面感应淬火硬度分别提高7%和34%，绝对磨损体积分别下降了13%和25%。实践证实，对轴端沟槽底部激光相变硬化处理方法较其他表面处理方法工艺简单，加工工件符合技术要求，试验结果对零件表面处理提供了可靠依据。     

可调90°偏振面旋转器

给出一种可调式90°偏振面旋转器。调整复合片快轴的夹角α,便能在可见光范围内使用.     

Characterization of hollow fiber membranes in a permeator using binary gas mixtures

We have studied the CO₂/CH₄ mixed gas permeation through hollow fiber membranes in a permeator. An approach to characterize the true separation performance of hollow fiber membranes for binary gas mixtures was provided based on experiments and simulations. Experiments were carried out to measure the retentate and permeate flow rates and compositions at each outlet. The influences of pressure drop within the hollow fibers, non-ideal gas behavior in the mixture and concentration polarization were taken into consideration in the mathematics model. The calculation results indicate that the net influence of the non-ideal gas behavior, competitive sorption and plasticization yields the calculated CO₂ permeance in a mixed gas permeator close to that obtained in pure gas tests. Whereas the CH₄ permeance is higher in the mixed gas tests than that in the pure gas tests, as the plasticization caused by CO₂ dominates the permeation process. As a result, the CO₂/CH₄ mixed gas selectivity is smaller than those obtained in pure gas tests at equivalent pressures.The calculated membrane performance shows little changes with stage cut if the effect of concentration polarization is accounted for in the calculation. The integration method developed in this study could provide more accurate characterizations of mixed gas permeance of hollow membranes than other estimation methods, as our model considers the roles of non-ideal gas behavior and concentration polarization properly.     

Hydrothermal Synthesis of Acicular Lead Titanate Fine Powders

A pure, acicular lead titanate (PbTiO₃) fine powder with a white color has been prepared by hydrothermal synthesis. It is a new phase of PbTiO₃ with I 4 symmetry, cell parameters of a = 12.358 Å and b = 14.541 Å, and a density of 6.80 g.cm⁻³. The influences of pH (12.5 to 14.4), Pb/Ti ratio (1.0 to 1.6) in the feedstock, reaction temperature (130° to 230°C), time (0.25 to 4 h), starting materials, and additives on the formation of acicular PbTiO₃ under hydrothermal conditions have been investigated. The acicular PbTiO₃ with I 4 symmetry, referred to as the PX phase, can be converted to the perovskite-type (PE phase) of PbTiO₃ at about 605°C while its acicular morphology is essentially unchanged. The preferable conditions for preparing pure acicular PX-phase PbTiO₃ are that the pH is 13.0 to 14.0, Pb/Ti ratio is >1.3, reaction temperature is 170° to 200°C, time is 0.5 to 1.0 h, titanium butoxide (Ti[O(CH₂)₃CH₃]₄) is the starting material, and poly(vinyl alcohol) is an additive. The acicular grain of the PX phase is usually less than 100 nm in diameter and more than 1000 nm in length.     

偏振模色散统计特性的研究

利用动态方程研究了偏振模色散矢量的统计特性 ,分别用统计系综和频率系综两种方法进行数值模拟。数值结果表明 ,统计系综和频率系综两种方法的结果一致。在大归一化距离条件下 ,均方根时延的平方随归一化距离线性变化 ;偏振模色散矢量的各个分量服从高斯分布 ,差分群时延服从麦克斯韦分布 ;偏振模色散矢量弥散于整个邦加球